The British government does not want academics from the London School of Economics who do not have UK passports to give Brexit briefings to officials, according to AFP.
LSE staff members have been briefing the Foreign Office on scenarios around leaving the European Union following June's referendum but the institution has now been told that submissions from non-British staff will not be accepted.
"Some of our experts who were contributing will not be able to contribute because they are not UK nationals," a spokesman for the LSE said after a complaint by Assistant Professor Sara Hagemann.
Ms Hagemann, who originally comes from Denmark, wrote on Twitter yesterday: "UK govt previously sought work & advice from best experts. Just told I & my colleagues no longer qualify as not UK citizens".
Ms Hagemann teaches at the LSE's European Institute, which she joined in 2009.
She has held research and policy positions in Brussels, Copenhagen and London, according to her biography on the LSE website.
In a statement, the university said: "The UK government regularly calls upon LSE's world-class academics for their advice on a range of issues.
"We believe our academics, including non-UK nationals, have hugely valuable expertise, which will be vital in this time of uncertainty around the UK's relationship with Europe and the rest of the world.
"Any changes to security measures are a matter for the UK government," the statement said.
Contacted by AFP, Britain's foreign ministry did not immediately comment.
British Prime Minister Theresa May has said she will initiate talks on leaving the European Union by the end of March, following a shock referendum in June in which Britain voted to end its 43-year membership.
One of the key issues in the referendum campaign was the impact of immigration on British society and May has said she plans to clamp down on EU migrant arrivals.
A government proposal to make businesses publish lists of foreign workers sparked fierce controversy this week after interior minister Amber Rudd revealed it at the Conservative party conference.